1. Field of the Invention
The present invention relates to electrical terminal blocks and, more particularly, to a screwless electrical terminal block for quick wire attachment thereto and detachment therefrom.
2. Description of the Prior Art
There exists a series of different electrical terminal blocks. Some use screw connectors including a screw around which the wire is wrapped with the screw being then tightened to secure the connection. In the art of printed circuit boards, it is important that the terminal blocks be small as an alternative to screw-type connectors, various screwless terminal blocks have been developed in which typically a bare end of the electrical conductor is simply inserted in an opening defined in the housing of the terminal block with an internal resilient spring clip interfering with the opening and being capable of being deflected out of the way by the introduction of the bare conductor end into the housing. The resilience of the spring clip returns it into contact with the bare end such as to produce an electrically conductive contact with an interior terminal of the housing. The spring clip locks the bare conductor end into position in the terminal block. Various systems are proposed to release the spring clip from the conductor such as to remove the latter from the terminal block.
For instance, U.S. Pat. No. 5,348,496 issued to Ludwig on Sep. 20, 1994 discloses, as best seen in FIGS. 4 to 6 (and especially FIG. 6), a push-wire connection where a cantilevered leaf spring 34 is biased towards the contact wall 30 such as to imprison therebetween the stripped portion 24 of the wire. A release key 40 can be inserted through release passage 38 by way of a translational displacement to deflect the spring or finger 34 away from the contact wall 30 such as to allow the stripped wire portion 24 to be removed from the wiring device, as best seen in FIG. 6.
In U.S. Pat. No. 4,759,726 issued to Naylor on Jul. 26, 1998, there is shown in FIGS. 3 and 4 a generally U-shaped electrical terminal 32 having an upper gripping element 34 which is adapted to be displaced by cam-lever 42 such as to selectively imprison or release a wire 66 with respect to the electrical terminal 32. The cam-lever 42 operates as a pure pivot as opposed to your rotatable knob. In FIG. 6, there is shown a series of terminal blocks 10 connected in a multiple terminal.
In U.S. Pat. No. 3,152,851 issued to McLaughlin on Oct. 13, 1964, an actuating member 60 can be pivoted to displace a resilient arm 44 away or towards a housing abutment 54 such as to selectively imprison or release a wire 32 with respect to the wiring device 10.
In German Patent Publication No. 2511444 published on Sep. 23, 1976 to Marquardt, a push button 10 can be translationally displaced along arrow 11 of FIG. 1 such as to displace a spring member 15 between wire engagement and wire release positions, as respectively illustrated in FIGS. 2 and 3.
In European Patent Publication No. EP-335,093-A published on Oct. 4, 1969 to Feller AG, an operating element 10 can be pivoted (see FIGS. 1 and 2) such as to act on a U-shaped spring 7 for permitting a wire 4 to be inserted in the housing 1. The operating element 10 by its position, provides a visual indication of a correct contact between the wire lead 4 and the contact element 6 of the housing Japanese Patent Publication No. JP-A-54-50992 published on Apr. 21, 1979 in the name of Matsushita Denko K. K. shows various designs, including that of FIG. 13 where a cammed handle 4 is used on a spring 8 to hold wires in a housing.
Japanese Patent Publication No. JP-A-1-130480 published on May 23, 1989 to Matsushita Electric Works Ltd. discloses a quick connecting terminal device where an electrode wire 13 inserted in a hole 14 may be held in the housing by a lock spring 3. When the conductor 13 is completely inserted, its tip presses a U-shaped portion 6 of a sound emitting spring 5 and the sound so emitted ensures that the conductor 13 has been fully inserted in the terminal device.
British Patent Publication No. GB-751,675 published on Jul. 4, 1956 in the name of Arrow Electric Switches Limited illustrates in FIG. 1 a wire lead 17 held in a terminal block by a gripping member 30. Release holes 17 and 19 are provided in the sides of the housing such that a stiff and thin elongated element (e.g. a nail) inserted therethrough will displace the gripping element 30, by lever action, sufficiently such as to free the wire end 40.